1. Field of the Invention
This invention relates to an active silicon carbide powder containing a boron component and to a process for producing the same. More particularly, it relates to an active silicon carbide powder containing a boron component as boron carbide or as a solid solution or the like, and to a process for producing the same.
2. Description of the Prior Art
Silicon carbide is used for various applications in addition to heat-resistant industrial materials due to its high hardness, excellent oxidation resistance, excellent corrosion resistance, excellent spalling resistance and excellent strength at high temperatures. Of those applications, wrapping materials, pigments or materials for forming the matrix of, for example, a refractory require the silicon carbide to have not only a fine particle size but also an increased activity. Therefore, a process of pulverizing silicon carbide as finely as possible and, in addition, adding boron or a compound thereof, in particular boron carbide, in an appropriate amount depending on the end-use have so far been used. Recently, a process for producing an active .beta.-type silicon carbide powder with a submicron particle size, which comprises uniformly incorporating a boron component, although in a slight amount, has been disclosed [e.g., as disclosed in Japanese Patent Application (OPI) No. 160,200/75 (The term "OPI" as used herein refers to a "published unexamined Japanese patent application."), corresponding to U.S. patent application Ser. No. 471,303, filed May 20, 1974]. However, difficulty arises in using the former process due to the lack of availability economically of a boron or boron carbide powder having the desired particle size and purity and due to mixing techniques or the like available. Further, difficulty in obtaining a starting material of fine silicon carbide itself which is preferred prevents the process from being put into practical use. On the other hand, applications of the latter process are limited since the content of the boron component, calculated as boron carbide, is as low as 1.3% by weight or less and, in addition, restrictions on production techniques, e.g., the preparation of the starting material is complicated and a special reactor is needed for synthesis, naturally limit the industrial utilization of the latter process.